Quick and Easy Sprite –Victorian Rush Hour - Cocos2d-x by Example Beginner's Guide - page 226

Platform collision logic
We have in place all the information we need to check for collision through the inline
methods found in Player and Block .
In this game, we'll need to check collision between the _player object's bottom side and
the block object's top side, and between the _player object's right side and the Block
class' left side. And we'll do that by checking the _player object's current position and its
next position. We are looking for these conditions:
The diagram represents the conditions for bottom side collision, but the same idea applies
to right side collision.
In the current position, the _player object must be above the top of the block or touching
it. In the next position, the _player object must be either touching the top of the block or
already overlapping it (or has moved past it altogether). This would mean a collision has
occurred.